This Phase 1 STTR will develop novel techniques for coronary sinus access. The coronary sinus provides unique anatomic and physiologic proximity to all four cardiac chambers and the coronary circulation. For example, the coronary sinus is used for left ventricular lead insertion for biventricular pacing or cardiac resynchronization. Mor than 100,000 such implants are estimated annually in the United States, and the procedure is Food and Drug Administration approved treatment for congestive heart failure. However, transvenous coronary sinus lead insertion fails in 8-13% of attempts because of angulation, valves, unstable locations, bad thresholds, and anomalous anatomy. Alternatives include surgical insertion of epicardial leads by thoracotomy or completely deferring this therapy. Epicardial lead insertion via thoracotomy is painful, with prolonged recovery in heart failure patients, and is particularly hazardous when adhesions encase the heart after prior surgery or myocardial infarction. Right parasternal mediastinotomy, developed for biopsy of intrathoracic tumors is a minimally invasive thoracotomy that has been used for endocardial pacing and could allow unique access to the coronary sinus inside the right atrium. However, introducers optimized for this purpose are lacking. The present STTR would develop three-dimensional image-configured introducers. Specific Aim1 will use magnetic resonance and X-ray computerized tomography imaging in patients to define geometry for coronary sinus cannulation. Cost-effective techniques for customized, patient-specific cannula design and manufacturing will be developed. Specific Aim 2 will test prototypes to refine designs and methods in six anesthetized pigs. Utility of steerable catheters and intracardiac echocardiography will be examined. Introducer technology will be derived and prototypes will be available for compassionate use and further development in Phase II. Milestones will be assessed at all stages of development. Preliminary experience of the research team suggests that this STTR will produce technical advances that will lead to successful commercial development. Improved coronary sinus access would facilitate diagnostic and therapeutic interventions including arrhythmia mapping and ablation, minimal access cardiac surgery, minimally invasive mitral valve surgery, mechanical circulatory assistance, and reduction of myocardial infarction size. Further development of percutaneous access techniques using imaging and tissue sealants could ultimately expand the market for these customized introducers to more than 300, ooo procedures annually.